The present invention relates to heat exchangers, and more particularly to a tube support structure for a tube and shell stream generator.
Tube and shell stream generators such as those used in nuclear power plants include a vessel containing a large number of stainless steel tubes affixed at their ends to tube sheets. The tubes are typically arranged in an equilateral triangular array and are supported at a number of positions along their length by support structures. Support structures for steam generators should hold the tubes rigidly to thereby supress vibration, should impose a minimum of resistance to the flow of fluid around the tubes, and should minimize the occurrence of crevices around the tubes where impurities may build up. Tube support structures of the prior art have to a large extent failed in one or more of these objectives. The orifice type support plate presented a high resistance to fluid flow. This type also suffered from a large number of crevices around the tubes. As impurities deposited and built up between a tube and the plate, the tube was pinched together. This phenomenon is commonly known as "denting".
The broached plate type tube support also suffers from the denting phenomenon albite to a far less degree than the orifice type plate.
Moreover, plate type supports are extremely expensive to fabricate and transport.
Other types of support structures include bars held between rows of the tubes. However, these structures are prone to flow induced vibrations resulting in damage to the tubes.